Updated: 6:02 a.m.Sen. Robert Byrd (D-W.Va.), the longest-serving Member in history, died at 3 a.m. Monday after a brief hospital stay. He was 92.I am saddened that the family of U.S. Senator Robert C. Byrd, D-W.Va., tearfully announces the passing of the longest serving member of Congress in U.S. history, Byrds office said in a statement.In a separate statement Sunday afternoon, his office said Byrd had been hospitalized after suffering from heat exhaustion and dehydration. He was described as being seriously ill."Byrd, who was first elected to the Senate in 1958, was President Pro Tem, a largely ceremonial post but one that put him third in succession to the presidency. Daniel Inouye (D-Hawaii) is next in line for the position.On Nov. 18, his 20,774th day of service in Congress, Byrd reached a milestone as the longest-serving lawmaker in Congressional history. He had previously held the title of the longest-serving Senator.He also served in every Senate leadership role, including as Majority Leader from 1977 to 1981 and from 1987 to 1989.Byrds health had been deteriorating: He had appeared increasingly frail and was forced to use a wheelchair for the past several years. Byrd spent several weeks in the hospital in May and June of last year, and he was rushed by ambulance to a hospital Sept. 22 after falling at his Northern Virginia home. On Sunday, his office announced he was in the care of a Washington-area hospital, where he was sent last week after suffering from heat exhaustion and dehydration.Byrds appearances in the Senate were spotty over the past year. He delivered an impassioned tribute on Sept. 10 to his late colleague Sen. Edward Kennedy (D-Mass.), who died of brain cancer on Aug. 25, and he took to the well of the chamber Oct. 21 to warn against heightened U.S. involvement in Afghanistan. He also was present in December for a dramatic vote held just past 7 a.m. on Christmas Eve to support President Barack Obamas signature health care overhaul, as well as for pivotal procedural votes leading up to its passage. Byrds profile rose following a deadly mining explosion in West Virginia in April, and he offered his influential opinion in the debate over the filibuster at a Rules Committee hearing in May. His most recent vote was June 10.Byrds age and health started to become problematic during the 110th Congress, when Senate Democrats feared that he no longer had the vigor to lead the powerful Appropriations Committee. After subtle nudging from leadership, Byrd voluntarily ceded the gavel in the 111th Congress to Inouye, his longtime friend and colleague.Still, over the span of his nine Senate terms, Byrd never lost the respect of his colleagues, no matter their political bent. He was a prolific legislator, an institutionalist and a passionate orator who never went anywhere without a pocket-size version of the Constitution, which he quoted regularly.Byrd came to the Senate after serving three terms in the House. Unlike many of his Congressional colleagues, he grew up poor and had no formal education. His appetite for learning was insatiable, however, and he developed a keen knowledge of Senate rules and procedures that was virtually unmatched by any other Senator.